1. Field of the Invention
The present invention belongs to the technical field of a printed circuit board that has conductive pads on the front side of a rectangular board and a connector that connects this printed circuit board. In particular, the present invention relates to measures or the like for improving the workability of connecting the printed circuit board to the connector.
2. Related Art
Printed circuit boards of this kind include, for example, those in which semiconductor chips such as semiconductor memories are mounted on rectangular board. A connector is used extensively, which connects a printed circuit board of this kind to a printed circuit board such as a mother board (hereinafter referred to as the counterpart board) in a position wherein the two boards are approximately parallel to each other. This connector has an approximately U-shaped form to correspond to the front side, left side and right side of the printed circuit board. A groove is formed in this connector to receive the front side of the printed circuit board. Plural contacts, which contact the conductive pads of the printed circuit board and clamp the printed circuit board, are provided in this groove. The connector has arms that extend backward to correspond to the left side and the right side of the printed circuit board. The top ends of these arms can undergo elastic deformation leftward and rightward, respectively, and each arm is provided with a engaging claw on the inner side of the top end thereof. This connector is mounted on the counterpart board by soldering the solder tails of the contacts onto the counterpart board. When the printed circuit board is to be fitted into the connector, first, the printed circuit board is set in the insertion/withdrawal position in which the rear end of the printed circuit board is lifted more in comparison with its level in the connection position, and the front side of the printed circuit board is inserted between the contacts. Next, the rear side of the printed circuit board is pushed downward. The conductive pads of the printed circuit board and the contacts will contact with each other. Moreover, the top ends of the arms will be pushed away outward, and the printed circuit board will slip under the engaging claws. The engaging claws returning to their respective initial positions will engage the left side and the right side of the printed circuit board. This will retain the printed circuit board in the connection position. When the fitted printed circuit board is to be disconnected from the connector, the top ends of the arms are made by fingers to undergo elastic deformation outward so as to disengage the engaging claws from the printed circuit board. Then the rear side of the printed circuit board will be lifted by the elastic restoring forces of the contacts and the printed circuit board will be shifted from the connection position to the insertion/withdrawal position. Thus the printed circuit board can be withdrawn from the space between the contacts.
There is a tendency, for the above-mentioned conventional connector, to set a high contact force between the conductive pads of the printed circuit board and the contacts so as to prevent defective contact or the like. As a result, a large force is needed to insert the printed circuit board into the contacts and this greatly reduces the connection workability. The increase in the number of the contacts aggravates the problem. The edges of the printed circuit board may damage the plated layers of the contacts or deform the contacts; such damages may lower the reliability of the connector. Furthermore, the conductive pads may be damaged. Such problems are common to any printed circuit boards that are to be inserted into the connector, irrespective of whether semiconductor memories are mounted on the boards or not.
One object of the present invention is to reduce the insertion force of the printed circuit board and improve the connection workability, and to eliminate any damages or the like to the contact and the conductive pad and enhance the reliability of the connector by providing a wedge-shaped auxiliary member for smoothly guiding the contacting surfaces of the contact onto the conductive pad of the printed circuit board.
On the other hand, semiconductor memories show a tendency to increase their heat generation significantly. It is due to, for example, quickening of their operating speed that is a result of the speed-up of the CPU. This thermal load may cause deformation of the connector, which in turn results in loss of the engaging function of the engaging members. Outward elastic deformation of the top ends of the arms by fingers may cause plastic deformation. Such loss of the engaging function and deformation may cause problems of defective connection and disconnection of the printed circuit board. Heat generation also poses a problem that it may make the operation of the semiconductor memories unstable. Moreover, if the connector is exposed to effects of ambient electromagnetic waves or the like, the operation of the circuits may become unstable. These problems are not limited to the connector that is used for printed circuit boards having semiconductor memories. Such problems are common to the connector that is used for printed circuit boards having general semiconductor chips.
Hence a connector that is effective in providing both thermal load countermeasures and electromagnetic wave countermeasures will be disclosed in the following.
To accomplish the above-mentioned objective, the cap for printed circuit board according to the present invention is a cap that is to be fitted onto a printed circuit board that has a conductive pad on the front side of a rectangular board and is to be connected to a connector. This cap is shaped into a bag that can be put over the front side of the printed circuit board, and is formed into a wedge so that the thickness thereof corresponding to the direction of board thickness of the printed circuit board is reduced towards the front. The cap has a window through which the conductive pad of the printed circuit board is exposed.
When this cap is put over the front side of the printed circuit board and the front side of the printed circuit board is inserted towards the contact, the contacting surface of the contact will be smoothly guided along the slope of the wedge-shaped cap into the window to come into contact with the conductive pad of the printed circuit board in the window. Thus, without reducing the contact force of the conductive pad of the printed circuit board and the contact, the insertion force of the printed circuit board is reduced and the connection workability is improved. Moreover, damages or the like to the contact and the conductive pad are eliminated and the reliability of the connector is enhanced. Similar effects may be obtained by chamfering the printed circuit board. Such chamfering, however, has drawbacks that the existing printed circuit boards can not be used directly, that beveling the edges of the front side of the printed circuit board may cause peeling of the conductive pad or scattering of the plated layers and, in turn, cause losses in terms of costs. In contrast to it, as the cap according to the present invention does not require any working on the printed circuit board, existing circuit boards can be used directly, and there will be no losses in terms of costs due to peeling of conductive pads and scattering of plated layers.
The low insertion force connector according to the present invention is a low insertion force connector that connects a printed circuit board having conductive pads on the front side of the rectangular board thereof, and this low insertion force connector comprises:
a connector body having at least a pair of contacts being to contact the conductive pads and clamp the printed circuit board;
a slider that is supported by the connector body so that the slider can be advanced to or retreated from the contacts and that is to carry and retain the printed circuit board; and
a wedge-shaped guide, which is provided on the front edge of the slider, of which rear end is continuous to the front side of the printed circuit board being on the slider, and of which thickness corresponding to the board thickness direction of the printed circuit board is reduced toward the front.
This low insertion force connector is mounted on a counterpart board by, for example, soldering the solder tails of the contacts onto the counterpart board. When the printed circuit board is placed on the slider and the slider is moved forward, the front side of the printed circuit board will be inserted into the contacts of the connector body. In the process, the contacting surfaces of the contacts will be guided smoothly along the slopes of the wedge-shaped guide onto the printed circuit board to contact the conductive pads. As a result, without reducing the contact forces between the conductive pads of the printed circuit board and the contacts, the insertion force of the printed circuit board can be reduced to improve the connection workability. Moreover, damages or the like to the contacts and conductive pads are eliminated, and the reliability of the connector is enhanced. When the slider is retreated, the printed circuit board will be withdrawn from the contacts. Similar effects can be obtained by chamfering the printed circuit board. This chamfering, however, has drawbacks that it can not be directly applied to the existing printed circuit boards, that beveling of the edges of the front side of the printed circuit board may cause peeling of the conductive pad and scattering of plated layers, and in turn, losses in terms of cost. In contrast to it, the low insertion force connector according to the present invention does not require working on the printed circuit boards, and the existing printed circuit boards can be used directly. Moreover, the connector is free of losses in terms of cost due to peeling of the conductive pad and scattering of plated layers.